Measuring resistors such as are used in arrangements for measuring currents, for example, are resistors which are connected in series into the electric circuit to be measured, the voltage dropped across said measuring resistor being used for determining the current intensity. In this case, with regard to precision, stringent requirements are made of measuring resistors, that is to say of the absolute accuracy of the resistance and the greatest possible independence with respect to temperature fluctuations. Both factors have a significant influence on the obtainable measuring accuracy of the current measuring arrangements.
These requirements constitute the major reason why measuring resistors in circuit arrangements for current measurement according to the prior art are predominantly embodied as discrete, external components. Alongside the absolute accuracy of the resistance which can be controlled very well in the case of discrete components, a low temperature dependence can also be achieved here by suitable selection of the materials, the construction and the production technology. The temperature dependence of a component is described by the temperature coefficient, which specifies the temperature drift per 1 kelvin. The unit ppm/K is customary in this case. A normal discrete metal film resistor has a temperature coefficient of 100 ppm/K, that is to say that it changes its resistance by 0.01% (100 ppm) for a temperature change of 1 kelvin. Discrete precision resistors, by contrast, drift only by a value of 25 ppm/K. The sensitivity of precision measuring devices to disturbing temperature influences should nevertheless be significantly reduced further by suitable active temperature correction of said precision measuring devices.
The continuously advancing demand for integration of components into semiconductor bodies with a small area requirement also relates to the integration of measuring resistors in semiconductor circuit arrangements for measuring the current intensity. The above-described factors of the absolute accuracy of the resistance and the greatest possible independence with respect to temperature fluctuations constitute the major challenges in this case, too. Due to the embodiment as a resistor structure in an integrated semiconductor body and the associated production-technological tolerances and also the temperature coefficients based on the material properties (silicon) used, in this case it is not possible, however, to achieve the precision with regard to resistance and temperature coefficient as known from discrete, external components.
In order to obtain the desired absolute accuracy of the resistance of a resistor structure integrated into a semiconductor body, it is known to integrate so-called laser fuses into said resistor structure in the production process. These are interruptible connection bridges in the resistor structure of the semiconductor body, which are severed in a targeted manner in order to obtain a precise adjustment of the resistor structure to the desired resistance. This is effected for example by the energy of a pulsed laser, for example a Neodymian YAG laser, which melts the metal track of the fuse arrangement locally, that is to say in a typical width of 2 to approximately 5 μm, and interrupts it in this way.
However, the temperature coefficient of such a resistor structure integrated into a semiconductor body according to the prior art is still subject to the production-technological tolerances and material properties inherent in the creation of semiconductor bodies and can influence the desired measurement results in an impermissible manner.